China has successfully launched a pair of navigation satellites to expand the nation's Beidou (Compass) system to global coverage.

The launch is the 33rd the country has undertaken this year and the ninth contributing to the Beidou project.

The four-hour mission placed the satellites in medium Earth orbit (MEO) on the back of one of China's Long March rockets.

Launching from Sichuan Province, at the Xichang Satellite Launch Centre (XSLC), the satellites are smaller than a car - measuring 2.25m by 1.22m by 1m.

They will form part of the Beidou Navigation Satellite System (BDS) which the Chinese government has designed and constructed to meet its own national security standards.

Speaking to Sky News Wu Weiqi, the deputy director for XSCL, told Sky News: "Under the demands of our society, under the needs of construction of modernization, and to meet people's desire for a better life, China has big demands to develop its own launch technology.

"China also has a blueprint for aerospace development, not only plans for manned space flight, but also has satellites planned for communication, navigation, climate prediction, earth environment monitoring."

Image:The two satellites offer China global navigational coverage

Xiejun, the chief designer of Beidou Navigation Satellite, told Sky News: "The Beidou navigation system is very key for the future of Chinese aerospace.

"Step by step, China is getting closer to US GPS in this sector. The successful development of the Beidou system marks Chinese aerospace's important development.

"But compared with US, navigation satellites are only one part of aerospace technology - we should also compete in other sectors too."

Speaking to Sky News about the security implications of the launch, Alexandra Stickings, space policy and security research analyst for think tank RUSI, said: "Global navigation satellite systems have become incredibly important for the military.

"What these systems do is provide very accurate navigation and timing systems. These are used for everything from maritime navigation to precision weaponry. It's what make smart bombs smart, essentially.

"The more that China is able to access these signals and the more accurate these signals become the more they can integrate that into their military, and then they could potentially start to rival the US in terms of precision military operations."

Image:The launch took place at Xichang Satellite Launch Centre

The BDS has been classed as providing 95% accuracy within six metres horizontally, and 95% accuracy within 10 metres vertically.

Navigation satellites are generally considered a shared global resource - with the American Global Positioning System (GPS) being among the most widely used.

A rival to GPS is being developed by the EU, called Galileo, and in the face of the UK potentially being frozen out of the Galileo project the prime minister announced that the country will develop its own satellite system.

While the satellite navigation systems are considered a public resource, the nations that operate them often reserve the most accurate bands of measurement for their own military uses.

Interference in GPS signals has become a significant threat for military forces and traditional map-reading and non-digital navigational skills are being stressed following suggestions that hostile nations are developing the capabilities to disrupt satellite navigation.

Earlier this month the Finnish prime minister suggested that air navigation services across the country had been interrupted by the Russian Federation due to a NATO exercise.

Russia denied the accusation, but had previously threatened to harm satellite navigation and on-board radars of combat aircraft which attacked target in Syria, following an apparent "friendly-fire" incident.